Guide and support structure

ABSTRACT

The invention relates to a guide and support structure ( 1 ) that in addition to providing a secure and stable guide support for the plug-in unit and good electric contact properties enhances the removal of heat from the plug-in unit. This is achieved by means of a guide and support structure having an upper web forming a guide channel for a plug-in unit and being connected to a base of the structure through side walls of the structure. The base is at least partially open in order to allow air flow through the interior of the elongated profile. By virtue of such a configuration blockage of a cooling-air flow will be significantly reduced. Such a reduced blockage of cooling-air flow will in turn enhance the cooling of plug-in units and will require less powerful fans for producing the cooling-air flow.

This application is a continuation of international applicationPCT/SE01/02747 filed Dec. 12, 2001 which designates the U.S.

TECHNICAL FIELD

The present invention relates generally to a structure for supportingelectronic component carriers, such as printed circuit cards, in achassis, such as an enclosure.

BACKGROUND

It has been common practice for many years to mount printed circuitboards or cards in enclosures as so called plug-in units that may beeasily inserted into and/or removed from the enclosure for replacementor repair. Conventionally, the plug-in units are slidably received inguide and support structures that are commonly named board guides orboard rails. The main purpose of the board guide is to securely guidethe plug-in unit into position in the enclosure, so that it may beconnected to the backplane of the enclosure. In its simplest form, theconventional board guide typically consists of a molded guide channelmanufactured from a non-conductive material and having integrally formedattachment means.

However, for most applications board guides are presently required toestablish electrical contact between a conductive pattern or layer onthe printed circuit board or card and a wall of a conductive enclosure.Such electrical contact or connection may be required both for thepurpose of employing the enclosure as ground for the operation of theseparate circuit boards and/or electronic components carried thereon andfor the purpose of eliminating or at least minimizing electromechanicalradiation emanating from the boards or cards.

Several attempts have been made to develop board guide structures thatwill meet the requirements for establishing an electrical connectionbetween the circuit boards and the enclosure. Typically, such furtherdeveloped board guides have a composite structure consisting of a solidchannel member accommodating a separate contact and/or guide member. Thesolid channel member is normally molded or extruded from a syntheticresin material and accommodates a contact and/or guide member havingseveral board contact spring fingers formed of a conductive metal. Thecontact and/or guide member is also provided with integral enclosurecontact means extending through openings in the channel member tocontact the enclosure. In other arrangements the channel member isformed of a thermally conductive material, such as aluminum, in order topromote heat transfer from the circuit board.

Examples of such prior art composite board guides are disclosed in U.S.Pat. Nos. 5,187,648, 5, 805,429 and 5,533,631.

U.S. Pat. No. 4,007,403 discloses a board guide that is formed as anintegral unit of for instance stainless steel. Accordingly, this boardguide eliminates some of the above discussed disadvantages. On the otherhand, it comprises very few board contact points, which means that areliable electrical contact with an inserted circuit board cannot beguaranteed.

In the board guides of the above discussed general designs it isdifficult to provide a reliable electrical contact between the board andthe enclosure and to maintain such contact during the useful life of theboard guide. For the composite design, the reason for this is mainly theseparate channel members and contact members. Specifically, the channelmember is typically attached to the enclosure and the enclosure contactmeans of the guide and/or contact member are clamped between the channelmember and the enclosure by said attachment. This means that cold flowor aging of the channel member material will directly affect theelectrical connection that is basically also rather unreliable due tothe fact that the contact is established only at the individual contactpoints of the board contact fingers and of the enclosure contact means.In this regard, the board guide design disclosed in U.S. Pat. No.4,007,403 is even more unreliable. Here, the electrical contact betweenthe board and the enclosure is restricted to the attachment means at thetwo ends of the structure, leaving the entire middle area of thestructure free of any positive attachment to a supporting enclosure.

For the same reason the heat transfer capacity of the conventional boardguide designs is quite limited, especially where the channel memberconsists of a resin material. In such board guides, the transfer of heatfrom the circuit board is restricted mainly to the limited contactpoints of the guide and/or contact member. Even in the above mentionedstructures where the channel member is formed as an extruded aluminumprofile or as an integral unit of stainless steel, the transfer of heatfrom the board to the channel member is restricted by the limitedcontact points. In the composite design heat transfer is also restrictedeven further by the often casual transfer from the guide and/or contactmember to the channel member.

Furthermore, the conventional board guides cause additional problems inapplications involving air-cooled enclosures. In such applications,cooling air flows through perforations in the enclosure walls to removeheat from the mounted circuit boards. In the above discussedconventional board guides a considerable portion of the flow of coolingair is effectively blocked by the guide structures having a rigid baseforming or supporting the channel or channel member, respectively. Thecomposite structure with the solid channel member as well as theintegral guide structure of U.S. Pat. No. 4,007,403, are also bothcomparatively wide, so that they cover and thus block a relatively largenumber of perforations. In view thereof, the use of such board guidedesigns necessitates the use of more powerful fans to produce therequired cooling-air flow through the walls of the enclosure.

SUMMARY

The invention overcomes the above problems in an efficient andsatisfactory manner.

A general object of the invention is to provide a solution to theproblem of providing an effective guide and support structure for aplug-in unit that is intended for slidable insertion into a chassis.

In particular, it is an object of the invention to provide an improvedguide and support structure that enhances the removal of heat from aninserted plug-in unit, in addition to maintaining a secure and stableguide and support for the plug-in unit and good electric contactproperties.

Briefly, this is achieved by means of a guide and support structurehaving an upper web forming a guide channel for a plug-in unit. Throughside walls of the structure, the upper web is connected to a base of thestructure. With such a configuration the guide and support structurewill be slim and will basically not cause any unnecessary blockage of acooling-air flow in a supporting chassis. Moreover, the base is at leastpartially open in order to allow air flow through the interior of thestructure. Such a partly open design of the base will additionallyreduce blockage of the cooling-air flow. This reduction of the blockageof cooling-air flow will in turn enhance the cooling of the plug-inunits and will require less powerful fans for producing the cooling-airflow.

In an embodiment of the invention, the guide and support structure isformed as an integral unit from an electrically as well as thermallyconductive metallic plate material. The metallic plate material will notonly provide the appropriate support and guide for the plug-in unit, butwill also secure good electrical contact throughout the useful life ofthe structure.

In another embodiment of the invention, the base of the guide andsupport structure has means for fixing the structure against the chassisas well as means for establishing electrical contact with the chassis.With such a configuration, good electric contact will be establishedboth with regard to the chassis and to the plug-in unit.

In another embodiment of the invention the guide and support structureis configured as an elongated profile having a base forming means forconducting heat from a plug-in unit to the chassis. By virtue of themetallic material, the guide and support structure will also act as aneffective heat sink.

In a practical embodiment the base of the guide and support structure isformed by free edges of the side walls, said free edges serving tosupport the structure against a chassis wall and to fix the structure tosaid wall as well as to provide the desired electrical and heatconducting contact therewith. Leaving the entire space between the sidewall edges open will provide maximum cooling-air flow into the interiorof the profile.

In a further embodiment of the invention the pressure drop of thecooling air flow caused by the guide and support structures of a chassisis reduced even further by providing apertures in at least one of theside walls of the elongated profile, said apertures serving to form apath for the cooling-air flow from the interior of the elongated profileto the interior of the chassis.

In other embodiments of the invention the guide and support structure isdesigned to provide a particularly secure guiding of the plug-in unitinto position and a particularly firm support of said plug-in unit in afixed position, and to provide a particularly effective electricalcontact between the plug-in unit and the guide and support structure.

In further embodiments of the invention, the guide and support structureis designed to provide possibilities for a rational manufacturing of theintegral guide and support structure, and to provide a secure attachmentof the entire guide and support structure to a chassis wall.

These and further objects of the invention are met by the invention asdefined in the appended patent claims.

In summary, the present invention provides the following advantages overthe state of the art:

A good electrical contact will be maintained at all times; thereby

Securing a reliable grounding of the plug-in unit; and

An effective shield against electromagnetic radiation;

The guide and support structure will secure an effective conduction ofheat from the plug-in unit, acting as a heat sink;

The guide and support structure causes minimum blockage of a cooling airflow, thereby further enhancing cooling of the plug-in unit;

The plug-in unit will be securely guided and supported in the structure;

The support unit is extremely easy to handle and to mount, consisting ofonly one unitary piece.

Other advantages offered by the present invention will be readilyappreciated upon reading the below detailed description of embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, maybest be understood by making reference to the following descriptiontaken together with the accompanying drawings, in which:

FIG. 1 is a top perspective view of a first embodiment of a guide andsupport structure according to the invention;

FIG. 2A is a partial perspective view of guide and support structuresaccording to FIG. 1 attached to a schematically illustrated chassis andguiding and supporting schematically illustrated plug-in units;

FIG. 2B is an enlarged view of a detail of the chassis illustrated inFIG. 2A, illustrating a slightly modified assembly of the guide andsupport structures;

FIG. 3 is a bottom plan view of the guide and support structure asillustrated in FIG. 1;

FIG. 4A is a cross section through the guide and support structureillustrated in FIGS. 1 and 3, taken along the line A—A of FIG. 3;

FIG. 4B is a cross section corresponding to that of FIG. 4A,illustrating the attachment of the guide and support structure to achassis wall and also schematically illustrating a carrier inserted intothe guide channel of the guide and support structure;

FIG. 5A is a partial bottom perspective view from one side of the firstembodiment of the guide and support structure;

FIG. 5B is a partial bottom perspective view from the opposite side ofthe first embodiment of the guide and support structure;

FIG. 6 is a cross section through a second embodiment of the guide andsupport structure according to the invention, taken along line B—B ofFIG. 8;

FIG. 7 is a partial bottom perspective view of the second embodiment ofthe guide and support structure illustrated in FIG. 6;

FIG. 8 is a bottom plan view of the second embodiment of the guide andsupport structure that is illustrated in FIGS. 6 and 7;

FIG. 9 is a cross section through a third embodiment of the guide andsupport structure according to the invention, taken along line C—C ofFIG. 11;

FIG. 10 is a partial bottom perspective view of the third embodiment ofthe guide and support structure illustrated in FIG. 9; and

FIG. 11 is a bottom plan view of the third embodiment of the guide andsupport structure that is illustrated in FIGS. 9 and 10.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention will be described below with reference to the drawingfigures that illustrate embodiments thereof adapted for use insupporting plug-in type PCB boards in a rack or sub-rack, such as in atelecommunications cabinet or magazine. However, it shall be understoodthat the invention is not restricted to this exemplifying embodiment orto such an application. The basic principles of the invention maylikewise be applied in association with guide and support structures forother carriers of electronic components and of the plug-in type.

Such alternative applications will cover any electronic componentcarrier of the plug-in unit type, such as printed circuit cards andelectronic modules, supported in an enclosure that may be referred to asa chassis, a cage or a rack and that accommodates an optional number ofsuch carriers. Therefore, modifications and variations of the inventionthat may be required in such applications fall within the scope of theinvention.

A first embodiment of the invention will now be described with specificreference to drawing FIGS. 1-5. FIGS. 1, 3, 4A-B and 5A-B illustrate apresently preferred embodiment of the inventive guide and supportstructure 1 for plug-in cards or boards, whereas FIGS. 2A and 2Billustrate the inventive guide and support structure in a typicalapplication for supporting plug-in units 2 in a sub-rack 20.

According to the invention, the guide and support structure 1, or boardguide, is formed as a generally U-shaped (see FIGS. 4A and 4B) elongatedprofile that is manufactured as an intgral unit from a metallic platematerial having good electrical as well as thermal conductivity. Apresently preferred material is a tin-plated stainless steel grade, butother metal plate materials having the appropriate properties maylikewise be employed.

The elongated profile 1 consists of two spaced but substantiallyparallel first and second profile side walls 7, 8 respectively that areinterconnected at one end by an upper web portion 9, where “upper”refers to its positioning, in the attached condition, with regard to thewall 21 or 22 of the sub-rack or chassis 20. The opposite or lower endsor free edges 7A, 8A of the side walls 7, 8 form a base portion 5 of theguide and support structure 1 (se especially FIGS. 5A and 5B). The baseportion is completely open between the free edges 7A, 8A and is intendedto be supported against a side wall 21 or 22 of the sub-rack 20 in theattached condition.

A guide channel 3 is formed in the upper web portion 9 of the profile 1,said guide channel likewise having a general U-shape, but being directedwith its open side facing away from the base portion 5 of the profile 1.The guide channel 3 serves the main purpose of securely guiding aplug-in unit 2 during insertion and of supporting the inserted unit 2 ina fixed position. In order to facilitate the initial insertion of aplug-in unit, an insertion ramp 3A is provided at the entrance to theguide channel 3, said ramp having an inclined surface and outwardlydiverging side walls. In fact, an insertion ramp 3A is provided at eachend of the guide channel 3, so that a plug-in unit 2 may be insertedfrom either end thereof. This adds to the flexibility of the guide andsupport structure, since it may be attached to a chassis in two invertedpositions. Furthermore, the appropriate guide and support for a plug-inunit in the guide channel 3 is achieved by providing a continuos rigidbottom wall 3B and likewise rigid first and second channel side walls 3Cand 3D, respectively. Said channel side walls 3C, 3D are continues, thatis uninterrupted, over at least an essential portion of their height(see especially FIGS. 4A, 5A and 5B). The second channel side wall 3Dhas a larger uninterrupted height than the first channel side wall 3C,for reasons that will be explained further below.

A series of individual contact members 4 are formed in the first profileside wall 7, evenly distributed along the length of the profile. To beprecise, the individual contact members 4 consist of a base portion 4Aand a contact portion 4B. The base portion 4A is formed basically fromthe plate material of said first profile side wall 7. The contactportion 4B is formed basically from the material of the web portion 9,which results in the above mentioned reduced uninterrupted height of thecorresponding first channel side wall 3C. The contact portion 4B has atapered and slightly rounded outer free end to allow insertion of aplug-in unit, as will be discussed below. In the illustrated embodiment,the base portion 4A of the contact members 4 is provided with a centralfirst side wall aperture 11 serving as a cooling-air exit, as willlikewise be discussed further below. This means that each base portion4A actually consists of two spaced support legs 4A together supporting acontact portion 4B. Each support leg 4A is bent inwardly towards theguide channel 3 at a position 4C adjacent their connections to theremaining first profile side wall 7. Thereby the contact portion 4B ispositioned at the proper position above the open side of the guidechannel 3 (FIGS. 4A and 4B), that is extending into the path of movementof an inserted plug-in unit.

Second side wall apertures 12 are provided in the second profile sidewall 8 and partly in the upper web 9, likewise serving as the laterdiscussed cooling-air exits. The second side wall apertures 12 that areformed in the second profile side wall 8 are wider in the longitudinaldirection of the profile 1 than the first side wall apertures 11 formedin the first profile side wall 7. On the other hand, the first side wallapertures 11 extend further down towards the base portion 5. In essence,the cooling-air exit area provided by the second side wall apertures 12approximately equals the combined cooling-air exit area provided by thefirst side wall apertures 11 and the open area surrounding the contactmembers 4.

At the base portion 5 of the profile 1, each one of the free edges 7A,8A of the side walls 7, 8 is provided with a number of locking tabs 6that are formed integral with the side walls and that protrudedownwardly therefrom, as seen in the illustrations of FIGS. 4A and 4B.In the illustrated embodiment he locking tabs 6 are evenly distributedalong each free edge 7A, 8A, with the locking tabs of one edge 7 beingdisplaced with half a pitch along said edge in relation to the lockingtabs of the other edge 8. Such an arrangement is presently regarded asproviding the best distribution for obtaining a secure attachment to asub-rack wall. However, other arrangements for the locking tabs 6 mayprovide an equally secure attachment and the invention shall thereforenot be restricted to such a specific positioning of the locking tabs. Inany specific practical application the arrangement of the locking tabsshall be adapted to the pattern of the perforations of the chassis wall,to ensure that in the correct position of the structure 1 all of thetabs 6 will fit properly into a corresponding perforation 23.

With specific reference to drawing FIGS. 4A-B and 5A-B, it will be seenthat each locking tab 6 comprises a generally V-shaped main body 6A. Afirst portion of the main body extends downwardly from the lower edge ofan associated side wall 7, 8 of the profile 1, substantially in theplane of said associated side wall. A second portion of the main body 6Ais bent outwardly and then back towards the associated side wall,forming an acute angle with the first portion. A support lug 6B isformed at the free end of the second portion by bending said free end tolie substantially in a plane that is transversal to the plane of theassociated side wall and that crosses said side wall at its lower freeedge. In the mounted condition said support lug 6B is intended to engagean inner surface of a wall 21 or 22 of a chassis 20. Furthermore, pawls6C are provided at each side of the first portion of the main body. Saidpawls are intended to engage an outer surface of said wall 21 or 22 ofthe chassis 20 to thereby fix the guide and support structure 1 to saidchassis wall.

It will be appreciated that with the above described design theinventive guide and support structure 1 may be manufactured in one piecein a very rational manner. In an initial step, the entire profile may bepunched from a metallic plate material in one single punching operation.Specifically, the free edges 7A, 8A of the side walls 7, 8, the lockingtabs 6, the individual contact members 4, the insertion ramps 3A and thefirst and second side apertures 11 and 12 may be formed in such aninitial step. In subsequent bending operations, the U-shaped guidechannel 3 is formed; the entire elongated profile 1 is given its generalU-shape; and the insertion ramps 3A, the contact members 4 and thelocking tabs are given their final shape.

FIG. 2A illustrates the use of the inventive guide and support structure1 in a typical air-cooled chassis or sub-rack 20 that is schematicallyillustrated by means of two walls 21, 22 thereof. The walls 21, 22 areprovided with evenly distributed perforations 23 that serve the doublepurpose of allowing cooling-air to enter the interior of the rack 20 tocool plug-in units 2 inserted therein and of maintaining an appropriateshield against electromagnetic radiation. The cooling-air flow istypically created by means of fans that are provided outside thesub-rack. This manner of providing a flow of cooling-air is conventionaland will not be discussed in any detail, nor illustrated any furtherherein.

With reference to FIG. 2A, pairs of guide and support structures 1 areprovided at the same level in the two walls 21 and 22, that is in thecorresponding rows of the perforations 23. FIG. 2A illustrates the guideand support structures 1 that are attached to the wall 21 beingpositioned to the right in said drawing figure. It should be understoodthough, that guide and support structures 1 are attached in the samemanner to the inner side of the wall 22 being positioned to the left inthe drawing figure. Said further guide and support structures 1 are onlyvaguely visible in FIG. 2A, represented by the locking tabs 6 extendingthrough the chassis 20 wall 22.

In order to attach the guide and support structures 1 to the chassis 20walls 21, 22, the locking tabs 6 are introduced into the appropriateperforations 23 of the walls 21, 22. Specifically, the locking tabs areinserted with the point of the V-shape first, until the support lugs 6Bengage the inner surface of the associated wall 21 or 22 and the pawls6C have been extended through the perforations 23 so as to be in aposition for engaging the outer surface of the wall. In this way, thechassis wall 21 will be clamped between the pawls 6C on the one hand andthe support lugs 6B and the free edges 7A, 8A of the side walls 7, 8 onthe other hand, as is clearly illustrated in FIGS. 3 and 4B. Thedistance W between the outer extremities of the two pawls 6C of eachlocking tab 6 slightly exceeds the diameter D of the perforations 23(see FIG. 3). This means that the side walls and/or the locking tabs ofthe guide and support structure 1 shall be elastically deformed wheninserting the locking tabs 6 into the perforations. Specifically, thisis done to position the pawls 6C approximately at the diameter of theassociated perforation, where they may be freely inserted. When thelocking tabs 6 have been fully inserted, the side walls and/or lockingtabs are released to allow them to spring back and to position the pawlsin a position where they both engage the outer surface of the chassiswall and positively lock the guide and support structure 1 to thechassis wall. In order to automatize the attachment of the guide andsupport structures 1 the necessary force for providing the elasticdeformation of the side walls and/or locking tabs is preferably appliedby means of a special tool that is not part of the invention and that isnot specifically disclosed herein.

Plug-in boards 2, normally having board fronts 2A, are then insertedinto the chassis 20 by being slidably introduced into the guide channels3 of the appropriate pairs of guide and support structures 1. Theinitial insertion is facilitated by the provision of the insertion ramps3A. The further insertion of the plug-in boards 2 will be in a directiontransversal to the individual contact members 4 that extend into thepath of the plug-in board. Through the tapered and slightly roundedouter free end of the contact members 3, the insertion of the plug-inboards 2 will cause the contact members to be elastically deflected fromsaid path of movement. With a plug-in board 2 fully inserted into aguide and support structure 1, all of the individual contact members 4will therefore assist in biasing the board 2 against the second higherchannel side wall 3D. A reliable electrical as well as thermal contactwill be established between the board 2 and the combination of theplurality of individual contact members ands the rigid second channelside wall 3D having the larger uninterrupted height and therefore havinga larger contact surface. The large surface area of the second channelside wall in combination with the continuos bottom channel wall 3B willalso secure that the board 2 is properly guided and positioned in theguide and support structure 1.

Furthermore, the described configuration of the guide and supportstructure 1 provides for an effective and secure electrical as well asthermal contact between the base 5 of the profile 1 and the chassis 20walls 21, 22. Specifically, the combination of the entire free ends 7A,8A of the side walls 7, 8 and the locking tabs 6 form a large effectivecontact surface. It will be appreciated that a very effective groundingof the plug-in board 2 will be achieved in this manner, through thecombination of the large continues contact surfaces and the reliableattachment of the structure to the chassis wall by means of the lockingtabs being formed integral with the contact means. It will likewise beappreciated that by manufacturing the entire guide and support structure1 as an integral unit from a thermally conductive material the structure1 will serve as an effective heat sink, especially so in combinationwith the discussed large contact surfaces relative to the plug-in unitas well as relative to the chassis walls.

In applications where the guide and support units 1 are employed inair-cooled sub-racks or chassis 20, it is desirable that the chassiswalls are as open as possible to allow the appropriate cooling-air flow.In such cases, cooling of the plug-in units will be further improved bythe extremely slim design of the structure 1. Specifically, the slimdesign blocks fewer per-forations than the conventionally designed boardguides, thereby permitting a larger un-interrupted flow of cooling-airthrough the chassis walls. This slim design is made possible by thedescribed configuration of the structure 1 being manufactured as anintegral unit from a metallic plate material.

The cooling-air flow is enhanced even further with the design of thedescribed first embodiment having a base portion 5 being totally openbetween the free edges 7A, 8A of the side walls 7, 8. This open bottomaperture is indicated with the reference number 10 in FIG. 4A. Withreference specifically to FIG. 4B, this means that cooling-air CA willenter the interior of the profile 1 through perforations 23 that wouldconventionally be blocked by the board guide structure. From theinterior of the profile 1 this cooling-air CA will exit the profilethrough the first and second side wall apertures 11, 12, therebyassisting in removing heat from the mounted plug-in units 2.Experimental tests have been performed with an air-cooled sub-rack beingfully equipped with plug-in units. Said tests have indicated that byemploying guide and support structures 1 of the inventive design thepressure drop across the rack walls will be reduced to approximately 40%of the pressure drop resulting from the use of conventional boardguides. This in turn means that the cooling-air flow through the rackwill be increased by 10-30%, or alternatively that less powerful andtherefore less expensive fans may be employed for a given application.

Drawing FIGS. 6-11 illustrate modified second and third embodiments ofthe inventive guide and support structure 100 and 200 respectively. Saidembodiments are particularly suitable for applications that require alarge contact surface between the structure and a chassis wall in orderto promote electrical contact and/or conduction of heat. The secondembodiment is illustrated in FIGS. 6-8 and mainly differs from the firstembodiment by the provision of a bottom wall 105 forming the base of thestructure 100. The bottom wall 105 extends between lower portions 107A,108A of the side walls of the elongated profile 100. Specifically, inthe illustrated embodiment the elongated profile 100 is likewisedesigned so that it may be punched out in one piece from a plate blank.Thus, the bottom wall 105 is formed integral with the first side wall107 and is bent inwardly from the lower portion 107A thereof, towardsthe lower portion 108A of the second side wall 108.

In the illustrated embodiment the bottom wall 105 is continuos exceptfor bottom apertures 110A that will be the result of forming the lockingtabs 106 provided at the lower end 107A of the first side wall 107. Saidlocking tabs 106, with their main body 106A, support lug 106B and pawls106C, are formed from the material of the bottom wall 105, whereas thelocking tabs at the lower end 108A of the second side wall 108 areformed in the same manner as by the first embodiment. Furthermore thefirst and second side wall apertures of the first embodiment have beenomitted, with the result that the second side wall 108 is connected tothe web 109 and the guide channel 103 along the entire length of theprofile 100, without any interruption. Also, the base 104A of thecontact members 104 extends the full width of the contact member and iscontinuously connected to the contact portion 104B. Except for thedescribed differences the structure 100 of the second embodiment isidentical to that of the first embodiment and need not be described anyfurther. However, it shall be emphasized that in applications requiringalso an enhanced cooling-air flow, the guide and support structure 100of the second embodiment may likewise be provided with side wallapertures like those of the first embodiment as well as with one or moreadditional bottom wall apertures 110B (indicated with dash-dot lines inFIG. 8).

Drawing FIGS. 9-11 illustrate a third embodiment of the guide andsupport structure 200. In this embodiment, the upper portion of theelongated profile 200 is identical to that of the first embodiment,whereas a bottom wall 205 like in the second embodiment forms the base205 of the profile. The main difference is that in the third embodimentthe locking tabs are formed as gripping hooks 206 that are punched outfrom the bottom wall 205, leaving bottom apertures 210A. Whereappropriate said bottom apertures might be supplemented by furtherbottom wall apertures 210B, as is outlined in FIG. 11. The grippinghooks 206 are formed approximately centrally in the bottom wall 205,with regard to the lower portions 207A, 208A of the side walls 207, 208,and are bent backwards toward the bottom wall 205 so as to be extendedin the longitudinal direction of the profile 200. With this design, thestructure 200 may be easily attached by positioning the free end of thehooks 206 in a perforation 23 and by then simply pushing the structure200 forward in the direction of the hooks. Each hook 206 will then beextended through the associated perforation 23 to grip the chassis wallfrom the outside.

Throughout the drawing figures, identical or corresponding parts of theguide and support structures of the different embodiments are given thesame basic reference numeral, but with the addition of 100 in the secondembodiment and 200 in the third embodiment.

In further modified, but not specifically illustrated embodiments of theinvention any of the illustrated guide and support structures mayalternatively be provided with only one side wall aperture formed ineither one of the walls of the profile. Such a design may be appropriatefor specific applications requiring less than maximum cooling-air flow.

It will be understood by those skilled in the art that variousmodifications and changes may be made to the present invention withoutdeparture from the scope thereof, which is defined by the appendedclaims.

What is claimed is:
 1. A guide and support structure forming a guidechannel for slidably receiving an edge of a plug-in unit, such as aprinted circuit card or electronic module, and having a base portionwith means for supporting the structure against a chassis, mutuallyspaced but generally parallel side walls extending outwardly from thebase portion and resilient contact members extending into the path ofmovement of a plug-in unit being inserted into the guide channel formaking electrical contact with the plug-in unit, characterized by anupper web portion connecting outward ends of the side walls, in that theguide channel is formed in the upper web portion and in that the baseportion is provided with at least one bottom aperture forming a pathwith minimum blockage for cooling air (CA) flow from outside thechassis, through perforated walls of the chassis and into the interiorof the structure.
 2. A guide and support structure according to claim 1,characterized in that the web portion, the side walls and the baseportion with the means for supporting the structure is one integral unitformed of a metallic plate material having good electrical as well asthermal conductivity.
 3. A guide and support structure according toclaim 2, characterized in that the integral unit has the general form ofan elongate plate profile and in that said base portion forms means forconducting heat from an inserted plug-in unit to said chassis.
 4. Aguide and support structure according to claim 1, characterized in thatthe base portion comprises means for fixing the structure to the chassisas well as means for establishing electrical contact with said chassis.5. A guide and support structure according to claim 1, characterized inthat the base portion (5) is formed by free edges of the side walls,said free edges being spaced from the upper web portion and forming saidmeans for supporting the structure as well as means for establishingelectrical contact with said chassis and means for conducting heat froman inserted plug-in unit to said chassis.
 6. A guide and supportstructure according to claim 5, characterized in that the base of theelongate profile is completely open between the free edges of the sidewalls.
 7. A guide and support structure according to claim 1,characterized in that at least one of the side walls, of the elongateprofile is provided with side apertures forming a path for cooling air(CA) from the interior of the structure through said side wall and tothe interior of the chassis.
 8. A guide and support structure accordingto claim 7, characterized in that side apertures forming a path forcooling air (CA) are provided in both side walls, surrounding the guidechannel.
 9. A guide and support structure according to claim 1,characterized in that the guide channel that is formed in the upper webportion has a general U-shape with the open side of the guide channelfacing away from the base portion of the elongate plate profile, in thatthe guide channel has a continuos bottom wall and continuous spacedchannel walls (3C, 3D; 103C, 103D; 203C, 203D) and in that individualresilient contact members extend from one of the side walls of theelongate profile into the path of movement of an inserted plug-in unit.10. A guide and support structure according to claim 9, characterized inthat the individual resilient contact members are formed partly from theplate material of one of the side walls and partly from the platematerial of the upper web portion.
 11. A guide and support structureaccording to claim 9, characterized in that the side apertures in one ofthe side walls of the elongate profile are formed through a base portionof each individual contact member.
 12. A guide and support structureaccording to claim 1, characterized in that the base portion is formedby a bottom wall extending between lower edge portions of the sidewalls, said bottom wall forming the means for supporting the structureas well as the means for establishing electrical contact with saidchassis and means for conducting heat from an inserted plug-in unit tosaid chassis.
 13. A guide and support structure according to claim 1,characterized by locking tabs protruding from the base portion, thelocking tabs being adapted for insertion into perforations in a wall ofthe chassis and forming said means for fixing the guide and supportstructure to the chassis as well as means for establishing electricalcontact with said chassis and means for conducting heat from an insertedplug-in unit to said chassis.
 14. A guide and support structureaccording to claim 13, characterized in that the locking tabs have ageneral V-shape with a first end thereof being integral with andextending from the free edge or from the edge portion of a respectiveside wall and with a second free end thereof forming a support lugintended for engaging the inner surface of a wall of the chassis and inthat the locking tabs adjacent said first end are provided with pawlsintended for engaging the outer surface of a wall of the chassis, tothereby fix the guide and support structure to said chassis wall.
 15. Aguide and support structure according to claim 14, characterized in thatthe locking tabs are provided with two pawls being extended in mutuallyopposite directions from side edges of the main portions of the lockingtabs.
 16. A guide and support structure according to claim 13,characterized in that the locking tabs are distributed at equaldistances from each other along each of the free edges or along each ofthe edge portions of the side walls and in that the locking tabs of oneside wall are displaced with half a pitch in relation to the lockingtabs of the other side wall.
 17. A guide and support structure accordingto claim 1, characterized in that the elongate profile is manufacturedfrom a stainless steel material that is tin plated.